Magnetic disc cartridge having a substrate with magnetized pit trains

ABSTRACT

A magnetic disc apparatus using a magnetic disc adapted so that recording and/or reproduction are carried out by a magnetic head unit which undergoes floating force by air flow produced as the result of the fact that the magnetic disc is rotated serves to selectively carry out loading of a first disc cartridge within which there is accommodated a first magnetic disc adapted so that flat recording tracks are provided at a disc substrate formed by molding synthetic resin and a magnetic layer is provided in a manner to cover the recording tracks, and a second disc cartridge within which there is accommodated a second magnetic disc adapted so that information uneven pit trains are formed at a disc substrate formed by molding synthetic resin and a magnetic layer is formed in a manner to include bottom surfaces and upper surfaces of information uneven pit trains, the magnetic layer being magnetized in the state where magnetization direction of the magnetic layer portions on the bottom surfaces and that of the magnetic layer portions of the upper surfaces of information pit trains are different from each other so that information such as program, etc. are recorded. Thus, new program can be installed into computer only by exchange of the disc cartridge.

TECHNICAL FIELD

[0001] This invention relates to a magnetic disc apparatus using, as arecording medium, a magnetic disc adapted so that a magnetic layer isformed on a disc substrate formed by molding synthetic resin, and a disccartridge within which a magnetic disc loaded into this magnetic discapparatus is accommodated, and more particularly to a magnetic discapparatus adapted so that a magnetic disc on which processinginformation processed by information processing equipment such ascomputer, etc. are recorded and a magnetic disc on which programinformation that computer executes are recorded in advance areselectively loaded, and a disc cartridge within which such a magneticdisc is accommodated.

BACKGROUND ART

[0002] Hitherto, as a recording device for recording processinginformation processed by computer, or for recording program informationthat computer executes, there are used disc apparatuses using, as arecording medium, hard disc which is magnetic disc using metallic discsubstrate of steel such as aluminum, etc. Such disc apparatuses are of astructure in which magnetic disc serving as recording medium isintegrally assembled within the apparatus body along with the magnetichead unit. In addition, disc apparatuses of this kind are used in thestate integrally assembled within the computer body.

[0003] In disc apparatuses adapted so that magnetic disc is integrallyassembled within the apparatus body in this way, since it is impossibleto exchange the magnetic disc, when there is necessity of recording newprogram information onto this magnetic disc, a magnetic disc unit forreproducing the magnetic disc on which such new program information arerecorded is required. Magnetic discs such as floppy disc can beexchangeably loaded with respect to such magnetic disc unit. Namely, itis necessary to carry out install operation which is an operation toread out new program information recorded on the magnetic disc by onemagnetic disc unit in which magnetic disc can be exchangeably loaded towrite the new program information thus read out onto magnetic discintegrally assembled within the other magnetic disc unit. Further, sincethe magnetic disc such as floppy disc has small memory capacity, a largenumber of magnetic discs are required for recording program informationof large information quantity. As a result, not only long time operationis required for install work, but also the work becomes complicated.

[0004] Moreover, in the case of recording processing informationprocessed by computer with respect to disc unit adapted so that magneticdisc is integrally assembled within the unit body, when memory capacityof the magnetic disc becomes small, it is necessary to erase datarecorded on the magnetic disc to ensure memory capacity. In the case ofstoring data erased from this magnetic disc, it is necessary to prepareanother recording unit capable of exchanging recording medium such asmagnetic disc or magnetic tape, etc. to record data with respect to thisrecording unit.

[0005] In the case where magnetic disc unit in which magnetic disc isintegrally assembled is used as a recording unit for computer as statedabove, it is necessary to further use another recording unit. As aresult, not only the computer becomes large-sized, but also installoperation of new program information and/or recording operation ofprocessing information processed by the computer become complicated.

[0006] Further, as a recording medium on which information processed bycomputer are recorded or program information that computer executes arerecorded, there are used CD-ROMs which are reproduction only typeoptical disc.

[0007] In CD-ROMs, pit trains formed as very small uneven trains at discsubstrate obtained by molding synthetic resin are used to recordprocessing information processed by computer and/or program informationthat computer executes. In the case of such CD-ROMs, stamper in whichpit trains corresponding to pit trains formed at the disc substrate areformed is prepared to allow this stamper to be loaded with respect tothe metal mold of the molding unit to mold synthetic resin, therebymaking it possible to manufacture a large number of the same CD-ROMs.

[0008] Since CD-ROMs can carry out high density recording, it ispossible to record a large quantity of processing information or a largecapacity of program information with respect to single CD-ROM.

[0009] Respective information recorded on the CD-ROM are read out byusing optical disc player provided with optical pick-up unit. Theoptical disc player serves to scan the signal recording surface ofCD-ROM rotationally operated after undergone loading with respect to thedisc rotational operation mechanism by light beams emitted from lightsource of optical pick-up unit to detect return light beams modulatedand reflected by pit trains of the CD-ROM by light detector providedwithin the optical pick-up unit to thereby read out respectiveinformation.

[0010] Meanwhile, since the optical disc player serves to scan, whilefocusing light beams emitted from the optical pick-up unit ontorecording tracks consisting of pit trains formed at the signal recordingsurface of the CD-ROM, recording tracks by these light beams to carryout read-out operation of information recorded on the CD-ROM, it isdifficult to quickly provide access to recording track at which desiredinformation is recorded. Thus, high speed read-out operation ofinformation cannot be carried out. Moreover, since the optical pick-upunit includes therewithin light source and light detector along withobjective lens for focusing light beams on the signal recording surfaceand objective lens drive unit for allowing the objective lens to undergodrive displacement, not only the weight is large so that this unitbecomes large-sized, but also it becomes difficult to carry out highspeed movement of the optical pick-up unit. As a result, it would becomedifficult to quickly provide access to recording track at which desiredinformation is recorded.

[0011] For this reason, in the case where information recorded on theCD-ROM is used in the computer, it is necessary for carrying out quickread-out operation of information to carry out smooth execution ofprogram to record such information onto hard disc adapted so that quickread-out operation of information can be carried out.

[0012] Also in the case where CD-ROM capable of carrying out highdensity recording and having large recording capacity is used as statedabove, it is necessary to carry out recording of information onto thehard disc. As a result, not only it becomes difficult to improveoperating ability of the computer, but also it is necessary to usemagnetic disc unit along with the optical disc player, thus allowing thecomputer to be large-sized.

DISCLOSURE OF THE INVENTION

[0013] An object of this invention is to provide a magnetic discapparatus which can improve operating ability of computer provided withrecording unit and realize miniaturization of computer.

[0014] Another object of this invention is to provide a magnetic discapparatus which can easily carry out supplement or exchange of programexecuted by computer.

[0015] A further object of this invention is to provide a magnetic discapparatus which can facilitate recording of processing informationprocessed by computer and storage of processing information.

[0016] A still further object of this invention is to provide a magneticdisc which can meet with such requirements that memory capacity can beincreased and discs on which the same information is recorded can beeasily mass-produced.

[0017] A still more further object of this invention is to provide amagnetic disc which can be loaded with respect to magnetic discapparatus after undergone positioning with high accuracy.

[0018] A further different object of this invention is to provide a disccartridge which can accommodate magnetic disc of which memory capacityhas been increased and can be selectively loaded with respect to themagnetic disc apparatus.

[0019] A still further different object of this invention is to providea disc cartridge which can easily discriminate kind of disc cartridge tobe loaded and a magnetic disc apparatus adapted so that such a disccartridge is loaded.

[0020] This invention is directed to a magnetic disc apparatus using amagnetic disc adapted so that recording and/or reproduction are carriedout by a magnetic head unit which undergoes floating force by air flowproduced as the result of the fact that the magnetic disc is rotated.This magnetic disc apparatus is adapted so that there are selectivelyloaded a first disc cartridge within which there is accommodated a firstmagnetic disc on which flat recording tracks are provided at a discsubstrate formed by molding synthetic resin and a magnetic layer isprovided in a manner to cover the recording tracks and a second disccartridge within which there is accommodated a second magnetic disc onwhich information uneven pit trains are formed at a disc substrateformed by molding synthetic resin, a magnetic layer is formed in amanner including bottom surfaces and upper surfaces of the informationuneven pit trains, the magnetic layer being magnetized in the statewhere magnetization direction of the magnetic layer portion of thebottom surface of the information pit train and that of the magneticlayer portion of the upper surface of the information pit train aredifferent from each other so that information such as program, etc. forcontrolling computer are recorded.

[0021] In this magnetic disc apparatus, the second disc cartridge withinwhich there is accommodated the second magnetic disc on whichinformation such as program, etc. for controlling computer are recordedis loaded, thereby making it possible to install new program withrespect to the computer.

[0022] The magnetic disc apparatus according to this invention furthercomprises a base adapted so that at least a disc rotational operationmechanism and a magnetic head unit are attached and a cartridge loadingportion is provided, and a casing within which the base is accommodated,wherein an insertion/withdrawal hole of the disc cartridge is providedat the casing, and the disc cartridge inserted into the casing throughthe insertion/withdrawal hole is loaded with respect to the cartridgeloading portion.

[0023] This magnetic disc apparatus further comprises, within thecasing, a cover opening/closing mechanism for allowing a cover bodywhich opens/closes an opening portion provided at the disc cartridge toundergo opening operation. In addition, at the magnetic disc unit, thereis further provided a cartridge discrimination mechanism fordiscriminating kind of disc cartridge loaded with respect to thecartridge loading portion.

[0024] As the second magnetic disc used in the magnetic disc apparatusaccording to this invention, there is used a disc including a discsubstrate adapted so that information uneven pit trains whereinformation are recorded and uneven pit trains for control where controlsignals for controlling positions of the magnetic head unit are recordedare formed on one surface and flat recording tracks are provided on theother surface, a magnetic layer formed in a manner including bottomsurfaces and upper surfaces of the information uneven pit trains and thecontrol uneven pit trains formed on one surface of the disc substrate,and a magnetic layer formed in a manner to cover recording tracks formedon the other surface of the disc substrate, wherein magnetization isimplemented to the magnetic layer formed on one surface of the discsubstrate in the state where magnetization direction of the magneticlayer portions of the bottom surfaces and that of the magnetic layerportions of the upper surfaces of the information pit trains aredifferent from each other so that information are recorded, andmagnetization is implemented to that magnetic layer in th state wheremagnetization direction of the magnetic layer portions of the bottomsurfaces and that of the magnetic layer portions of the upper surfacesof the control uneven pit trains so that control signals are recorded.

[0025] Further, at the magnetic disc used in this invention, there isprovided a hub mechanism including a pair of holding members attached tothe disc substrate in a manner to hold or put therebetween theperipheral edge of a center hole provided at the central portion of thedisc substrate and a clamping member of metal attached to these holdingmembers and clamped with respect to the disc rotational operationmechanism, wherein the pair of holding members of this hub mechanism areformed by synthetic resin having substantially the same coefficient ofthermal expansion as that of the disc substrate.

[0026] A disc cartridge loaded with respect to the magnetic discapparatus according to this invention comprises a cartridge body withinwhich there is rotatably accommodated either one of a first magneticdisc adapted so that flat recording tracks are provided on at least onesurface of a disc substrate formed by molding synthetic resin and amagnetic layer is provided in a manner to cover the recording tracks,the first magnetic disc being adapted so that recording and/orreproduction are carried out by a magnetic head unit comprising amagnetic head element provided at a slider caused to undergo floatingforce by air flow produced as the result of the fact that the magneticdisc is rotated and a second magnetic disc adapted so that there areprovided a disc substrate formed by molding synthetic resin and adaptedso that information uneven pit trains where information are recorded anduneven pit trains for control where control signals for controllingposition of the magnetic head unit are recorded are formed at least atone surface of the disc substrate, and a magnetic layer formed in amanner to include the bottom surfaces and upper surfaces of theinformation uneven pit trains and the control uneven pit trains, themagnetic layer being magnetized in the state where magnetizationdirection of the magnetic layer portions of the bottom surfaces and thatof the magnetic layer portions of the upper surfaces of the informationpit trains are different from each other so that information arerecorded, the magnetic layer further being magnetized in the state wheremagnetization direction of the magnetic layer portions of the bottomsurfaces and that of the magnetic layer portions of the upper surfacesof the control uneven pit trains so that control signals are recorded,the second magnetic disc being adapted so that recording and/orreproduction are carried out by a magnetic head unit comprising amagnetic head element provided at a slider adapted to undergo floatingforce by air flow produced as the result of the fact that the magneticdisc is rotated; an opening portion for insertion of the magnetic headunit provided at one side surface of the cartridge body; a cover bodyfor opening/closing this opening portion; and a central opening portionfor allowing at least the central portion of the magnetic disc to befaced toward the external.

[0027] The opening portion provided at the cartridge body is opened orclosed by a cover body provided at the front of the insertion directionside into the magnetic disc apparatus of the cartridge body, androtatably supported with respect to the cartridge body so that it can berotated in a direction in parallel to the plane surface of the cartridgebody and biased by a biasing member in a direction to close the openingportion. At this cover body, there is provided an engagement portionengaged with a cover body opening member provided at the magnetic discapparatus side when the disc cartridge is inserted into the magneticdisc apparatus.

[0028] Still further different objects of this invention and morepractical merits obtained by this invention will become more apparentfrom the description of the embodiments which will be explained below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1(A) and 1(B) are plan views showing a first magnetic discused in a magnetic disc apparatus according to this invention.

[0030]FIG. 2 is a plan view showing, in an enlarged manner, processinginformation recording area and control signal recording area of thefirst magnetic disc.

[0031] FIGS. 3(A) and 3(B) are plan views showing a second magnetic discused in the magnetic disc apparatus according to this invention.

[0032]FIG. 4 is a plan view showing, in an enlarged manner, processinginformation recording area and control signal recording area of thesecond magnetic disc.

[0033]FIG. 5 is a cross sectional view showing, in an enlarged manner,disc substrate and magnetic layer of each of the first and secondmagnetic discs.

[0034]FIGS. 6 and 7 are cross sectional views showing the state wheremagnetization is implemented to the first and second magnetic discs.

[0035]FIG. 8 is a perspective view showing disc cartridge within whichthe first or second magnetic disc is accommodated.

[0036]FIG. 9 is an exploded perspective view of the disc cartridge.

[0037]FIG. 10 is a longitudinal cross sectional view of the disccartridge.

[0038]FIG. 11 is an exploded perspective view showing cover bodyprovided at the disc cartridge and upper half to which this cover bodyis attached.

[0039]FIG. 12 is a perspective view showing discrimination portionprovided at the disc cartridge and specification informationdiscrimination mechanism for detecting this discrimination portion.

[0040]FIG. 13 is a perspective view showing another example of disccartridge within which the first or second magnetic disc isaccommodated.

[0041]FIG. 14 is a perspective view showing the state where headinsertion opening portion provided at cartridge body of the disccartridge is opened.

[0042]FIG. 15 is a partial front view of the disc cartridge showing thestate where the head insertion opening portion is closed by the coverbody.

[0043]FIG. 16 is a side view of the disc cartridge showing the statewhere the head insertion opening portion is closed by the cover body.

[0044]FIG. 17 is a perspective view showing a magnetic disc apparatusaccording to this invention.

[0045]FIG. 18 is a perspective view showing recording/reproduction unitof the magnetic disc apparatus according to this invention.

[0046]FIG. 19 is a perspective view showing slider constituting magnetichead unit constituting the magnetic disc apparatus.

[0047]FIG. 20 is a side view showing the state where head slider towhich magnetic head element is attached undergoes floating force.

[0048]FIG. 21 is a side view showing the state where first or seconddisc cartridge is loaded with respect to the magnetic disc apparatus.

[0049]FIG. 22 is a side view showing the state where the first or seconddisc cartridge is inserted into the magnetic disc apparatus.

[0050]FIG. 23 is a side view showing the state where the first or seconddisc cartridge is inserted into the magnetic disc apparatus so that headinsertion opening portion is opened.

[0051]FIG. 24 is a perspective view showing the state where the first orsecond disc cartridge is loaded with respect to cartridge loadingportion of the recording/reproduction unit.

BEST MODE FOR CARRYING OUT THE INVENTION

[0052] A magnetic disc apparatus and a disc cartridge within whichmagnetic disc is accommodated, which is loaded with respect to suchmagnetic disc apparatus, according to this invention will be describedbelow.

[0053] The magnetic disc apparatus according to this invention serves tocarry out reproduction of information or control signals recorded on themagnetic disc, or to carry out recording of processing informationprocessed by computer by using a magnetic head device which undergoesfloating force by air flow produced as the result of the fact that themagnetic disc is rotated.

[0054] Magnetic disc used in this magnetic disc apparatus will now bedescribed.

[0055] With respect to the magnetic disc apparatus according to thisinvention, a first magnetic disc 1 onto which processing informationprocessed by information processing unit such as computer, etc. can berecorded and a second magnetic disc 15 on which program information thatcomputer executes are recorded in advance are selectively loaded. Thesefirst and second magnetic discs 1, 15 are formed in the state wherediameter is caused to be substantially 65 mm and thickness is caused tobe substantially 1.2 mm.

[0056] The first magnetic disc 1 onto which processing information canbe recorded will now be described. The first magnetic disc 1 comprises adisc substrate, which takes disc shape, formed by molding syntheticresin such as non-magnetic polyolefine system resin, etc. by injectionmolding unit. At least at one of one surface and the other surface ofthis disc substrate, there are provided processing information recordingareas 2 where processing information processed by information processingunit such as computer, etc. are recorded, and control signal recordingareas 3 where control signals for controlling position with respect tothe first magnetic disc 1 of the magnetic head unit which scans therecording area of the first magnetic disc 1 are recorded.

[0057] On the surface where the processing information recording areas 2and the control signal recording areas 3 are provided of the discsubstrate, there are formed magnetic layers magnetized in accordancewith processing information and control signals to be recorded.

[0058] Further, concentrical or spiral projected line portions in whichthe upper surface is caused to be flat surface are formed within theprocessing information recording area 2. These projected line portionsare caused to be recording tracks 4 where processing information arerecorded as shown in FIG. 2. At both sides of each projected lineportion, there are formed recessed line portions along the projectedline portions. These recessed line portions are used as guard bandportions 5 for preventing crosstalk of processing information recordedat recording tracks 4 adjacent to each other.

[0059] In addition, within the control signal recording area 3, thereare formed uneven pit trains for control where there are recordedcontrol signals for controlling positions of the magnetic head unit sothat the magnetic head element of the magnetic head unit which scans thesignal recording area of the first magnetic disc 1 precisely scans therecording tracks 4.

[0060] In more practical sense, as shown in FIG. 1, the first magneticdisc 1 is adapted so that its one circumference is partitioned into 60sectors. Each sector consists of 14 segments and one circumference iscaused to be 840 segments. In addition, each segment consists of theprocessing information recording area 2 and the control signal recordingarea 3.

[0061] Further, at the leading portion of the recording tracks 4provided in the processing information recording area 2, there isprovided ID recording area where track Nos. and sector Nos. arerecorded, which carry out discrimination of processing informationrecorded at the recording tracks 4. In addition, processing informationrecorded at the recording tracks are recorded into the informationrecording area succeeding to the ID recording area.

[0062] Further, within the control signal recording area 3 of the firstmagnetic disc 1, there are provided, as shown in FIG. 2, a burst portion6 comprised of uneven pit trains where there are recorded burst signalsused for auto gain control, etc. for controlling output of recording orreproduction signal in carrying out recording and/or reproduction ofprocessing information, a clock mark portion 7 comprised of uneven pittrains serving as reference of recording or reproduction of processinginformation, a track address portion 8 comprised of uneven pit trainsused in the case where scanning position of the magnetic head element 10is determined when the magnetic head unit carries out seek operation,and a fine pattern portion 9 comprised of uneven pit trains for carryingout positioning so that the magnetic head element 10 scans predeterminedrecording tracks 4.

[0063] Namely, the clock mark 7 is uneven pit train for generating clockserving as reference in recording or reproducing processing information,and clock is obtained in correspondence with reproduction signalobtained when the magnetic head element 10 scans this clock mark 7. Thisclock mark 7 is radially formed in the radial direction of the magneticdisc 1.

[0064] For the track address portion 8, gray codes are used. In morepractical sense, at the first magnetic disc 1, direction ofmagnetization is inverted in correspondence with 1 bit at gray code torecord track address onto the recording track 4. Namely, the reason whygray code is used as track address is as follows. Different bit of codesrecorded at adjacent recording tracks 4, i.e., codes adjacent to eachother is only 1 bit. Even in the case where the magnetic head element 10traverses two recording tracks 4, value reproduced from the magnetichead element 10 indicates either one of addresses of these two recordingtracks. Accordingly, employment of gray code is convenient in the seekoperation of the magnetic head device.

[0065] The fine pattern portion 9 is disposed in a manner shifted towardthe inner circumferential side and the outer circumferential side withcentral portion 11 between the recording tracks 4 being puttherebetween, and is formed in a manner spaced by a predetermineddistance also in the track direction. Thus, the magnetic head element 10is operative so that when it reproduces the fine pattern portion 9, itoutputs position pulses in correspondence with respective correspondingedges. Further, by carrying out the tracking control so that levels ofthese position pulses are equal to each other, the magnetic head element10 is controlled so that it is positioned on the center lines 11 betweenthe respective recording tracks 4.

[0066] The first magnetic disc 1 constituted in this way is operative sothat when it reproduces processing information recorded at the recordingtrack 4, the first magnetic disc 1 is caused to undergo tracking controlso that the magnetic head element 10 is positioned on the center line 11of the recording track 4 with the fine pattern portion 9 being asreference. Further, the first magnetic disc 1 is caused to undergotracking control, at the time of recording of processing information, onthe basis of tracking error signal obtained when the magnetic headelement 10 reproduces the fine pattern portion 9, thus permitting themagnetic head element 10 to scan along the respective center lines 11 ofthe recording tracks 4. Since the first magnetic disc 1 is formed so asto record sector Nos. or track Nos. in advance in this way, it ispossible to securely reproduce sector Nos. or track Nos. irrespective ofthe positioning state of the magnetic head element 10.

[0067] In this example, control signal of the magnetic head unitrecorded in advance in the control signal recording area 3 is recordedby magnetizing the magnetic layer which covers the uneven pit trainsprovided in the control signal recording area 3 so that magnetizationdirection of the magnetic layer portions on the upper surfaces of theuneven pit train and magnetization direction of the magnetic layerportion on the bottom surfaces thereof are different from each other.

[0068] The reproduction only type second magnetic disc 15 on whichinformation such as program information, etc. that computer executes arerecorded in advance will now be described.

[0069] This second magnetic disc 15 also comprises, a disc substratewhich takes disc shape, formed by molding synthetic resin such asnon-magnetic polyolefine system resin, etc. by injection molding unitsimilarly to the first magnetic disc 1. At least one surface and theother surface of this disc substrate, there are provided, as shown inFIG. 3, program information recording areas 16 where program informationthat computer executes and/or processing information processed bycomputer are recorded in advance, and control signal recording areas 17where control signals for controlling positions with respect to thesecond magnetic disc 15 of the magnetic head unit which scans therecording area of the second magnetic disc 15 are recorded.

[0070] Further, on the surface where the program information recordingareas 16 and the control signal recording areas 16 are provided of thedisc substrate, there are formed magnetic layers magnetized inaccordance with the program information and the control signals whichhave been recorded.

[0071] Further, within each program information recording area 16, thereare provided information recording tracks 18 comprised of informationuneven pit trains where program information are recorded in advance. Atboth sides of the information recording tracks 18 comprised of unevenpit trains, recessed line portions are formed along the recording tracks18. These recessed line portions are used as guard band portions 19 forpreventing crosstalk of information such as program information, etc.recorded at recording tracks 18 adjacent to each other.

[0072] Further, within the control signal recording area 17, there areformed uneven pit trains for control where there are recorded controlsignals for controlling positions of the magnetic head unit so that themagnetic head element 10 of the magnetic head unit which scans thesignal recording area of the second magnetic disc 15 precisely scans theinformation recording tracks 18.

[0073] In more practical sense, the second magnetic disc 15 is adaptedas shown in FIG. 3 so that its one circumference is partitioned into 60sectors. Each sector consists of 14 segments and one circumference iscaused to be 840 segments. In addition, each segment consists of programinformation recording area 16 and control signal recording area 17.

[0074] Further, at the leading portion of the recording tracks 18provided in the program information recording area 16, there is providedID recording area where track Nos. and sector Nos. for carrying outdiscrimination of information such as program information, etc. recordedat these recording track 18 are recorded. In addition, information suchas program information, etc. recorded at the recording tracks arerecorded in the information recording area succeeding to the IDrecording area.

[0075] Further, within the control signal recording area 17 of thesecond magnetic disc 15, there are provided, as shown in FIG. 4,similarly to the control signal recording area 3 provided in thepreviously described first magnetic disc 1, burst portion 6 comprised ofuneven pit trains where there are recorded burst signals used in autogain control, etc. for controlling output of recording or reproductionsignal in carrying out recording and/or reproduction of processinginformation, clock mark portion 7 comprised of uneven pit trains servingas reference of recording or reproduction of processing information,track address portion 8 comprised of uneven pit trains used fordetermining scanning position of the magnetic head element 10 when themagnetic head unit carries out seek operation, and fine pattern portion9 comprised of uneven pit trains for carrying out positioning so thatthe magnetic head element 10 scans respective predetermined recordingtracks 18.

[0076] The second magnetic disc 15 constituted in this way is operativeso that when information such as program information, etc. recorded atthe recording track 18 are reproduced, it is caused to undergo trackingcontrol so that the magnetic head element 10 is positioned on the centerline 11 between the recording tracks 18 with the fine pattern portion 9being as reference. Since the second magnetic disc 15 is formed in amanner to record sector Nos. or track Nos. in advance as stated above,it is possible to securely reproduce sector Nos. or track Nos.irrespective of positioning state of the magnetic head element 10.

[0077] Information such as program information, etc. recorded in advancein the program information recording area 16 of the second magnetic disc15 and control signals of the magnetic head unit recorded in advance inthe control signal recording area 17 are recorded by magnetizing themagnetic layers which cover uneven pit trains formed in the programinformation recording areas 16 and the control signal recording areas 17so that magnetization direction of the magnetic layer portions on theupper surfaces and that of the magnetic layer portions on the bottomsurfaces of the uneven pit train are different from each other.

[0078] Meanwhile, step differences of uneven portions between projectedline portions constituting recording tracks 4 formed in the processinginformation recording areas 2 of the first magnetic disc 1, uneven pittrains where control signals are recorded in advance, formed in thecontrol signal recording area 3 of the first magnetic disc 1, pit trainswhere information such as program information, etc. are recorded inadvance, formed in the program information recording area 16 of thesecond magnetic disc 15, and uneven pit trains where control signals arerecorded in advance, formed in the control signal recording area 17 ofthe second magnetic disc 15, i.e., heights of the convex portion areformed so that they are substantially equal to each other.

[0079] This is because when the first and second magnetic discs 1, 15are selectively loaded with respect to common magnetic disc unit tocarry out rotational operation thereof, substantially the same floatingforces can be produced with respect to the slider to which the magnetichead element is attached of the magnetic head unit provided at themagnetic disc unit side.

[0080] By forming the first and second magnetic discs 1, 15 so thatsubstantially constant floating force can be produced with respect tothe slider to which the magnetic head element is attached, even in thecase where any one of magnetic discs 1, 15 is loaded with respect to onemagnetic disc unit, distance between the magnetic head element and thesignal recording surface of the first or second magnetic disc 1 or 15becomes constant, thus making it possible to obtain reproduction outputof the same level. In this example, heights of the projections of thefirst and second magnetic discs 1, 15 are caused to be approximately 200nm.

[0081] The second magnetic disc 15 of the reproduction only type onwhich there are recorded in advance information such as programinformation, etc. that computer executes used in the magnetic disc unitaccording to this invention may be adapted so that the other surfaceside thereof is caused to be information recording surface which permitsrecording of information such as processing information, etc. processedby information processing equipment such as computer, etc. similarly tothe previously described first magnetic disc. By providing informationrecording surface on the other surface in this way, it is possible tofurther record information such as program information, etc. recorded onthe other recording medium such as optical disc, etc. Thus, wideusability as the magnetic disc can be improved.

[0082] The first and second magnetic discs 1, 15 using the discsubstrate formed by molding synthetic resin in a manner as describedabove are manufactured as follows.

[0083] Initially, in order to form the first or second magnetic disc 1or 15, a disc substrate 29 constituting the disc 1 or 15 is formed. Thedisc substrate 29 is formed by injection-molding synthetic resin such asnon-magnetic polycarbonate resin, polyolefine system rein, etc. Withrespect to at least one of fixed metal mold and movable metal moldconstituting cavity of metal mold unit which carries out forming of thisdisc substrate 29, stamper in which there are formed uneven patternscorresponding to projected line portions, recessed line portions anduneven pit trains formed at the disc substrate 29 is attached. Byinjecting synthetic resin into the cavity of the metal mold unit towhich this stamper is attached, disc substrate 29 to which the projectedline portions, the recessed line portions and/or uneven pit trainscorresponding to uneven patterns provided at the stamper are transferredis molded.

[0084] At the central portion of the disc substrate 29 molded here, acenter hole adapted so that a hub mechanism 58 is attached thereinto isprovided in a manner as described later. This center hole is formed bypunching the injection-molded disc substrate by punch provided at themetal mold unit side in releasing that disc substrate from the metalmold unit.

[0085] On the disc substrate 29 formed by using the metal mold unit inthis way, magnetic layers 30 are then formed. In order to form eachmagnetic layer 30, as shown in FIG. 5, a particle layer 31 in whichparticles (spherical silica) consisting of SiO₂ are caused to haveparticle density of 0.5 to 100, preferably about 10 per 1 μm is formedon the surface of the disc substrate 29. By forming this particle layer31, rigidity of the disc substrate 29 formed by synthetic resin isenhanced. In addition, the surface of the disc substrate 29 becomessmooth as the result of the fact that the particle layer 31 is provided.

[0086] Further, as shown in FIG. 5, a chromium layer 32 having thicknessof about 80 nm is formed on the upper layer of the particle layer 31.This chromium layer 32 functions as exchange coupling film andadvantageously improves the magnetic characteristic. Particularly, thechromium layer 32 can enhance coercive force. Further, a cobalt-platinumlayer 33 which is magnetic body having thickness caused to be about 40nm is formed on the upper layer of this chromium layer 32. Further, aprotective layer 34 having thickness of about 10 nm is formed on theupper layer of this cobalt-platinum layer 33. This protective layer 34is formed, e.g., SiO₂, and is formed by spin coat or coating. Inaddition, lubricant 35 is coated on the upper layer of this protectivefilm 34.

[0087] Magnetization is implemented to the magnetic layer 30 provided onthe disc substrate 29 thus constituted in a manner as described above.Thus, information such as program information, etc. and control signalsare recorded.

[0088] In order to implement magnetization to the magnetic layer 30, asshown in FIG. 6, disc substrate 29 on which magnetic layer 30 isprovided is loaded with respect to a magnetizing unit 40 to rotate thisdisc substrate 29 in a direction indicated by arrow A in FIG. 6.Further, a first d.c. current is applied to a magnetic head 41 formagnetization while moving the magnetic head 41 for magnetization of themagnetizer 40 in the radial direction of the disc substrate 29 tomagnetize the magnetic layer 30 which covers uneven pit train formed atthe disc substrate 29. At this time, the magnetic layer portions ofbottom surfaces 20 a and those of upper surfaces 20 b of the uneven pittrain are magnetized in the same direction. Then, a second d.c. currenthaving current value which is small as compared to the first d.c.current is applied, in the state having polarity opposite to the firstd.c. current, to the magnetic head 41 for magnetization while rotatingthe disc substrate 29 in the direction indicated by arrow A in FIG. 7,and while moving the magnetic head 41 for magnetization in the radialdirection of the disc substrate 29 to magnetize the magnetic layer 30portions of the upper surfaces 20 b of the uneven pit train of the discsubstrate 29. Namely, as the result of the fact that the magnetic layer30 is magnetized so that magnetization direction of the magnetic layerportions of the bottom surfaces 20 a and that of the magnetic layerportions of the upper surfaces 20 b of the uneven pit train aredifferent from each other, information such as program information, etc.and/or control signals are recorded onto the magnetic layer 30.

[0089] As stated above, information such as program information, etc.and/or control signals can be recorded by using single magnetic head 41and those information/signals can be recorded by magnetizing themagnetic layer so that magnetization direction of the magnetic layerportions on the bottom surfaces 20 a and that of the magnetic layerportions of the upper surfaces 20 b of the uneven pit train aredifferent from each other. Accordingly, those information/signals can beeasily recorded without carrying out exchange of magnetic head 41 formagnetization. Particularly, since large capacity of information such asprogram information, etc. can be recorded at a stroke by using singlemagnetic head 41 for magnetization, it extremely becomes easy tomanufacture a large number of the reproduction only type second magneticdiscs 15 on which information such as program information, etc. arerecorded in advance.

[0090] The first or second magnetic disc 1 or 15 constituted asdescribed above is constituted as disc cartridge accommodated within thecartridge body, and is loaded with respect to the magnetic disc unit inthe state accommodated within the cartridge body.

[0091] First disc cartridge 50 within which the first magnetic disc 1 isaccommodated and second disc cartridge 51 within which the secondmagnetic disc 15 is accommodated will now be described.

[0092] These first and second disc cartridges 50, 51 are different onlyin kind of magnetic discs to be accommodated, but are common in othermain configuration.

[0093] As shown in FIGS. 8 and 9, each of the first and second disccartridges 50, 51 includes a cartridge body 54 formed by butt-joining apair of upper and lower rectangular halves 52, 53, and is adapted torotatably accommodate the first magnetic disc 1 or the second magneticdisc 15 within this cartridge body 54. At one side surface of thecartridge body 54, there is provided a head insertion opening portion 55into which the magnetic head unit provided at the magnetic disc unit isadmitted. This opening portion 55 is opened or closed by a cover body 56rotatably attached at the cartridge body 54.

[0094] With respect to each of first and second magnetic discs 1, 15respectively accommodated within the first and second disc cartridges50, 51, there is attached a hub mechanism 58 for clamping each of thefirst and second magnetic discs 1, 15 with respect to the discrotational operation mechanism provided at the magnetic disc unit sideas described later.

[0095] The pair of upper and lower halves 52, 53 constituting thecartridge body 54 are formed by molding synthetic resin like ABS resinhaving satisfactory moldability and sufficient mechanical strength. Atthe periphery of these upper and lower halves 52, 53, there are providedrising circumferential walls 61 a, 61 b. These rising peripheral walls61 a, 61 b are butted to each other in the state where the upper half 52and the lower half 53 are combined to constitute the outercircumferential wall of the cartridge body 54.

[0096] Moreover, within the upper and lower halves 52, 53, there arevertically provided disc accommodating walls 62 a, 62 b in circular arcform which constitute a disc accommodating portion 63 in a mannerinscribed to the respective rising circumferential walls 61 a, 61 b.These disc accommodating walls 62 a, 62 b are butted to each other whenthe upper half 52 and the lower half 53 are combined to constitute thedisc accommodating portion 63. This disc accommodating portion 63 servesto limit accommodating position of the first or second magnetic disc 1or 15 accommodated therewithin and to ensure space for allowing themagnetic head unit to be admitted thereinto.

[0097] Moreover, at the central portion of the lower half 53, as shownin FIG. 9, there is formed a disc table admission opening portion 64into which disc table constituting the disc rotational operationmechanism of the magnetic disc unit is admitted. Further, the hubmechanism 58 attached to the first or second magnetic disc 1 or 15 iscaused to be positioned at the disc table admission opening portion 64.

[0098] The hub mechanism 58 attached to the first or second magneticdisc 1 or 15 is attached in such a manner to hold the peripheral edge ofthe center hole 57 formed at the disc substrate 29 therebetween fromupper and lower directions. This hub mechanism 58 is composed of a pairof upper and lower hubs 67 and 68 formed of synthetic resin material andserving as holding member for holding the disc substrate 29 therebetweenfrom upper and lower directions, and a metallic clamping member 69attached to the lower hub 68.

[0099] In this example, the first or second magnetic disc 1 or 15 towhich the hub mechanism 58 is attached is adapted so that an outercircumferential side non-signal recording area 71 is provided at theouter circumferential side of a recording area 70 where processinginformation recording area 2 or program recording area 16 and controlsignal recording areas 3 or 17 are formed, and an inner circumferentialside non-signal recording area 72 is provided at the innercircumferential side of the recording area 70 and in the areasurrounding the peripheral edge of the center hole 57.

[0100] As shown in FIGS. 9 and 10, the upper hub 67 constituting the hubmechanism 58 is formed so as to have height slightly greater than eachthickness of the first and second magnetic discs 1, 15, and is composedof a cylindrical first fitting portion 75 having bottom fitted into thecenter hole 57 of the disc substrate 29, a first flange portion 76provided in a projected manner at the periphery of the bottom endportion side of the first fitting portion 75, and a holding portion 77projected at the front end surface of the first fitting portion 76. Thefirst fitting portion 75 is formed in the state where it has outerdiameter substantially equal to the inner diameter of the center hole 57in such a manner that it is tightly fitted into the center hole 57provided at the disc substrate 29. The first flange portion 76 is formedso as to have diameter slightly smaller than the inner circumferentialside non-signal recording area 72 constituted at the peripheral edge ofthe center hole 57. As shown in FIG. 10, the upper hub 67 constituted inthis way is attached to the disc substrate 29 in the state where thefirst fitting portion 75 is fitted into the center hole 57 and the firstflange portion 76 is held in the inner circumferential side non-signalrecording area 72.

[0101] Moreover, the lower hub 68 is composed of a second fittingportion 78 formed cylindrical, which is fitted into the first fittingportion 75 of the upper hub 67, and a second flange portion 79 projectedat the periphery of the base end portion side of the second fittingportion 78. The second fitting portion 78 is formed so as to have heightcorresponding to quantity projected from the other surface of the discsubstrate 29 when the first fitting portion 75 is attached from onesurface side of the disc substrate 29. The second flange portion 79 isformed so as to have diameter slightly smaller than the innercircumferential side non-signal recording area 72 constituted at theperipheral edge of the center hole 57. The lower hub 68 constituted inthis way is attached in the state fitted into the first fitting portion75 and caused to be in contact with the inner circumferential sidenon-signal recording area 72 of the other surface side of the discsubstrate 29.

[0102] At the front end surface side of the second fitting portion 78 ofthe lower hub 68, there are projected holding portions 77 formed at thebottom surface of the first fitting portion 75 of the upper hub 67 side.Further, a clamping member 69 formed by thin metallic plate is attachedto the holding portions 77. Plural engagement holes 80 provided incorrespondence with the holding portions 77 are bored at this clampingmember 69. Moreover, at the clamping member 69, a spindle hole 81 isbored at the central portion thereof. Spindle constituting the discrotational operation mechanism is engaged into this spindle hole 81.Further, as shown in FIG. 10, with respect to the upper hub 67 and thelower hub 68, the clamping member 69 is fixed to the disc substrate 29by using ultrasonic welding or adhesive agent in the state where theholding portions 77 are held at the engagement hole 80.

[0103] Meanwhile, the upper hub 67 and the lower hub 68 constituting thehub mechanism 58 are formed by synthetic resin having substantially thesame coefficient of thermal expansion as that of the disc substrate 29constituting each of the first and second magnetic discs 1, 15. Namely,the upper hub 67 and the lower hub 68 are formed by synthetic resin suchas polycarbonate resin, polyolefine system resin, etc. similar to thatof the disc substrate 29. It is desirable that the disc substrate 29 andthe upper and lower hubs 67, 68 are formed by using the same syntheticresin. Further, in more practical sense, it is desirable that the discsubstrate 29 and the upper and lower hubs 67, 68 are formed by syntheticresin having coefficient of thermal expansion of 6.5 to 7.5×10⁻⁵ deg⁻¹.

[0104] By forming the upper hub 67 and the lower hub 68 in this way,thermal deformation of the first and second magnetic discs 1, 15 due todifference of thermal expansion with respect to the disc substrate 29can be suppressed. Thus, improvement in the recording/reproductioncharacteristic can be made.

[0105] Moreover, at the cartridge body 54, as shown in FIGS. 8 and 9, anopening portion 55 for insertion of head into which the magnetic headunit constituting the recording/reproduction means provided at themagnetic disc unit side is admitted is provided at the side surface ofthe insertion direction side into the magnetic disc unit. This headinsertion opening portion 55 is constituted by forming cut portions 82a, 82 b at respective portions of the rising circumferential walls 61 a,61 b formed at the periphery of the upper and lower halves 52, 53. Atthe head insertion opening portion 55, as shown in FIGS. 8 and 11, thereis attached a cover body 56 which is opened only in the case where thefirst or second disc cartridge 50 or 51 is caused to undergoinsertion/withdrawal with respect to the magnetic disc unit. This coverbody 56 comprises a shutter portion 85 for closing the head insertionopening portion 55, a supporting portion 86 rotatably supported at theupper half 52, and an arm portion 87 which connects the shutter portion85 and the supporting portion 86. The shutter portion 85 is formed so asto have semicircular shape substantially corresponding to the outershape of each of the first and second magnetic discs 1, 15 as a whole,and is formed so that its height substantially becomes equal tothickness of the cartridge body 54. At one end portion of this shutterportion 85, as shown in FIG. 11, there is projected a projected portion88 toward the external. At the shutter portion 85, guide shafts 89 a, 89b are provided in upper and lower directions of the end portion wherethe projected portion 88 is provided. These guide shafts 89 a, 89 b areengaged with guide recessed portions 90 a, 90 b formed at the innersurface side of the upper and lower halves 52, 53. The supportingportion 86 is adapted so that a fitting hole 92 fitted with respect to acylindrical supporting portion 91 provided in the central area of theupper half 52 is provided at the center thereof. The shutter portion 85and the supporting portion 86 are connected by a fan-shaped arm portion87 extended along the radial direction of each of the magnetic discs 1,15.

[0106] The cover body 56 constituted in this way is rotatably supportedwith the supporting portion 91 being as center in the state wheresupporting portion 91 of the upper half 52 is fitted into the fittinghole 92. A torsion coil spring 93 is fitted with respect to the outerperiphery of the supporting portion 91. This torsion coil spring 93 isheld between the supporting portion 92 and a portion of the cover body56 to rotationally bias the cover body 56 in a direction to close thehead insertion opening portion 55 with the supporting portion 91 beingas center. In this example, the cover body 56 is supported in the statepressed onto the internal surface of the upper half 52 by a set screw 95fixed to the upper half 52 through a metallic plate 94. On the otherhand, the guide shafts 89 of the shutter portion 85 are engaged with aguide recessed portion 90 formed in the vicinity of recessed portions 82a, 82 b of the upper and lower halves. Further, the cover body 56 isadapted so that when the first or second disc cartridge 50 or 51 iscaused to undergo loading with respect to the magnetic disc unit, theprojected portion 88 is caused to undergo pressing operation by thecover body releasing mechanism provided at the unit side, whereby thecover body 56 is rotated against biasing force of the torsion coilspring 93 to open the head insertion opening portion 55.

[0107] Moreover, at the upper half 52, there is provided, at the cornerportion of the front side thereof, a discrimination hole 98 indicatingkind or specification of the magnetic disc to be accommodated. Thisdiscrimination hole 98 indicates whether corresponding disc cartridge iseither first disc cartridge 50 within which first magnetic disc 1 whichcan record information such as processing information of computer, etc.is accommodated or second disc cartridge 51 within which second magneticdisc 15 of the reproduction only type on which information such asprogram information, etc. are recorded in advance is accommodated.

[0108] This discrimination hole 98 is opened in the case of, e.g., thefirst disc cartridge 50 within which first magnetic disc 1 which permitsrecording of information is accommodated, and is closed in the case ofthe second disc cartridge 51 within which the reproduction only typesecond magnetic disc 15 is accommodated. Thus, discriminationtherebetween is carried out. Discrimination between the first disccartridge 50 and the second disc cartridge 51 is carried out by aspecification information discrimination mechanism 100 provided at themagnetic disc unit as shown in FIG. 12, for example. In thisspecification information discrimination mechanism 100, a detectionswitch 99 is provided at position corresponding to the discriminationhole 98 provided at the first or second disc cartridge 50 or 51, andadapted to be fitted into the discrimination hole 98 when the first orsecond disc cartridge 50 or 51 is loaded with respect to the cartridgeloading portion of the magnetic disc unit. Further, discriminationbetween the first disc cartridge 50 and the second disc cartridge 51 iscarried out in dependency upon whether or not the detection switch 99 ofthe specification information discrimination mechanism 100 is admittedinto the discrimination hole 98.

[0109] First and second disc cartridges 101, 102 within which theabove-described first and second magnetic discs 1, 15 used in themagnetic disc apparatus according to this invention are respectivelyaccommodated may be constituted as shown in FIGS. 13 and 14.

[0110] Each of the first and second disc cartridges 101, 102 shown inFIGS. 13 and 14 includes a cartridge body 105 formed by butt-joining apair of upper and lower rectangular halves 103, 104, and is adapted torotatably accommodate the first magnetic disc 1 or the second magneticdisc 15 within the cartridge body 105. At one side surface of theinsertion side with respect to the magnetic disc unit of the cartridgebody 105, there is provided a head insertion opening portion 106 intowhich the magnetic head unit provided at the magnetic disc unit isadmitted. This opening portion 106 is closed by a cover body 107rotatably attached in a direction perpendicular to the plane surface ofthe cartridge body 105.

[0111] The cover body 107 for opening/closing this head insertionopening portion 106 includes a front panel 107 a for closing the headinsertion opening portion 106, and a pair of attachment pieces 107 b,107 c projected in a direction perpendicular to the front plate 107 a onboth sides of this front plate 107 a. This cover body 107 is rotatablyattached at the cartridge body 105 with support shafts 108, 108projected on faces opposite to each other of the attachment pieces 107b, 107 c being as the center by inserting the support shafts 108, 108through or into pivotal holes 109, 109 provided at side surfacesperpendicular to one side surface where the head insertion openingportion 106 is formed of the cartridge body 105 so that they aresupported, whereby they are rotatably attached with respect to thecartridge body 105 with the support shafts 108, 108 being as the center.Further, the cover body 107 is rotationally operated with the supportshafts 108, 108 being as the center to thereby open or close the headinsertion opening portion 106. The cover body 107 is rotationally biasedin a direction to close the head insertion opening portion 106 by springmember disposed within the cartridge body 105 although not shown.

[0112] Further, at the cover body 107, as shown in FIGS. 13, 14 and 15,there is formed an opening/closing pin engagement portion 111 formed bycutting the portion extending from the front plate 107 a toward oneattachment piece 107 b, the engagement portion 111 being adapted so thatopening/closing pin 110 constituting the opening/closing mechanism ofthe cover body provided at the magnetic disc unit side is engagedtherewith. As shown in FIG. 16, this opening/closing pin engagementportion 111 is formed at position deviating or shifted toward the sidewhere the cover body 107 is rotated in a direction to open the headinsertion opening portion 106 relative to the rotation center positionO₁ with the support shafts 108, 108 being as the center.

[0113] In addition, the cover body 107 is adapted so that when it islocated at the position where the head insertion opening portion 106 isclosed, the lock member 112 disposed within the cartridge body 105 isengaged with the opening/closing pin engagement portion 111, whereby thecover body 107 is locked at the position where the head insertionopening portion 106 is closed. The lock member 112 is adapted so thatwhen the first or second disc cartridge 101 or 102 is loaded withrespect to the magnetic disc unit, it is rotationally operated by theopening/closing pin 110 engaged with the opening/closing engagementportion 111, whereby engagement with the cover body 107 is released sothat there results the state where the cover body 107 can be rotatedwith the support shafts 108, 108 being as the center.

[0114] In this example, also in the first or second disc cartridge 101or 102 shown in FIG. 13, discrimination hole 98 indicating kind orspecification of magnetic disc to be accommodated is provided at thecartridge body 105.

[0115] A magnetic disc apparatus 201 according to this invention willnow be described. This magnetic disc unit 201 is of a structure in whichfirst or second disc cartridge 101 or 102 constituted as shown in FIGS.13 and 14 is loaded therewithin.

[0116] As shown in FIG. 17, the magnetic disc unit 201 according to thisinvention comprises a casing 202 constituting the unit body. Within thiscasing 202, there is disposed a recording/reproduction section 203 inwhich the first or second disc cartridge 101 or 102 is loaded to carryout recording/reproduction of processing information with respect to thefirst magnetic disc 1 accommodated within the first or second disccartridge 101 or 102, and to carry out reproduction of programinformation recorded on the second magnetic disc 15.

[0117] Further, at the front side of the casing 202, there is providedan insertion/withdrawal hole 200 for carrying out insertion/withdrawalof the first or second disc cartridge 101 or 102 loaded with respect tothe magnetic disc unit 201.

[0118] As shown in FIG. 18, the recording/reproduction section 203disposed within the casing 202 comprises a base 211 comprised ofmetallic plate consisting of aluminum alloy, etc. At the upper surfaceside in FIG. 18 of this base 211, there is constituted a cartridgeloading portion 204 adapted so that the first or second disc cartridge101 or 102 inserted into the casing 202 through the insertion/withdrawalhole 200 is loaded after undergone positioning. Further, at the centralportion of the base 211, there is disposed a disc rotational operationmechanism 205 for allowing the first or second magnetic disc 1 or 15accommodated within the first or second disc cartridge 101 or 102 loadedwith respect to the cartridge loading portion 204 to undergo rotationaloperation. This disc rotational operation mechanism 205 is composed of adisc table 205 a on which the first or second magnetic disc 1, 15 isintegrally clamped through the hub mechanism 58, and spindle motor forallowing this disc table 205 a to undergo rotational operation. The disctable 205 a is rotated in the direction indicated by arrow R₁ in FIG. 18at constant angular velocity by the spindle motor.

[0119] Moreover, on the base 211, there is disposed a magnetic head unit210 for carrying out recording and/or reproduction of information withrespect to the first or second magnetic disc 1, 15 caused to undergorotational operation in the state clamped by the disc rotationaloperation mechanism 205. This magnetic head unit 210 comprises arotational arm 213 for supporting a head slider 216 adapted so thatmagnetic head element 10 is integrally attached at the front end sidethereof, and a voice coil motor 217 for allowing the rotational arm 213to undergo rotational operation.

[0120] The rotational arm 213 is rotated, in the state where the middleportion thereof is supported by a support shaft 212 vertically providedon the base 211, in the direction indicated by arrow R₂ and in thedirection indicated by arrow R₃ in FIG. 18 with the support shaft 212being as the center. Further, the head slider 216 is attached through aleaf spring 215 connected to the front end side of the rotational arm213. This leaf spring 215 is formed so that it is caused to undergoelastic displacement in a direction to come into contact with the signalrecording surface of the first or second magnetic disc 1 or 15 clampedby the disc rotational operation mechanism 205 or to become awaytherefrom.

[0121] The voice coil motor 217 is composed of a drive coil 218 attachedat the base end portion side of the rotational arm 213, and a magnet 219disposed on the base 211 in a manner opposite to this drive coil 18.This voice coil motor 217 rotates the rotational arm 213, with thesupport shaft 212 being as the center, in the direction indicated byarrow R₂ and in the direction indicated by arrow R₃ in FIG. 18 by actionbetween drive current delivered to the drive coil 218 and magnetic fieldof the magnet 219. When the rotational arm 213 is caused to undergorotational operation, the head slider 216 attached to the front side ofthis rotational arm 213 is caused to undergo movement operation alongthe inner and outer circumferences of the first or second magnetic disc1 or 15, whereby the magnetic head element 10 attached to this headslider 216 scans the signal recording area of the first or secondmagnetic disc 1 or 15 to carry out recording of processing informationwith respect to the first magnetic disc 1, or to carry out read-outoperation of program information recorded on the second magnetic disc.

[0122] In this example, the magnetic head unit 210 is adapted so thatwhen it is located at the initial position where it does not carry outrecording and/or reproduction of information with respect to the firstor second magnetic disc 1 or 15, the front end side of the leaf spring215 which has supported the head slider 216 is caused to be supported onthe supporting portion 220 provided on the base 211. By supporting theleaf spring 215 in this way, it is limited that the leaf spring 215 iscaused to inadvertently undergo displacement, thus to prevent that thehead slider 216 and the magnetic head element 10 attached to the headslider 216 come into contact with foreign matter so that they aredamaged.

[0123] Meanwhile, at the head slider 216, as shown in FIG. 19, a pair ofside rails 230 a, 230 b which form air bearing are formed between thehead slider 216 and the first or second magnetic disc 1 or 15 on bothsides of the lower surface side opposite to the first or second magneticdisc 1 or 15 to form a recessed portion 231 between these side rails 230a, 230 b. These side rails 230 a, 230 b are adapted so that when thehead slider 216 is opposed to the surface of the first or secondmagnetic disc 1 or 15, they are formed in a manner substantially inparallel to recording tracks 4 or 18 formed at the first or secondmagnetic disc 1 or 15. At the air inlet end side opposite to therotational direction of the first or second magnetic disc 1 or 15 of theside rails 230 a, 230 b, there are formed taper portions 232 a, 232 b.In addition, the magnetic head element 10 is provided at the end portionof air outlet side opposite to the air inlet side of the head slider216.

[0124] When the head slider 116 constituted in this way is caused to beclose to the surface of the first or second magnetic disc 1 or 15 causedto undergo rotational operation as shown in FIG. 20, the head slider 116undergoes floating force produced by air flow caused to flow into theportion between side rails 230 a, 230 b and the surface of the first orsecond magnetic disc 1 or 15 followed by rotation of the first or secondmagnetic disc 1 or 15 so that it is caused to float from the surface ofthe first or second magnetic disc 1 or 15. When the head slider 216floats from the surface of the first or second magnetic disc 1 or 15,the magnetic head element 10 attached to this head slider 216 is causedto also float from the surface of the first or second magnetic disc 1 or15 as shown in FIG. 20, and it moves along inner and outercircumferences on the first or second magnetic disc 1 or 15 with afloating quantity of very small distance D₁, e.g., about 0.1 μm beingheld between the magnetic head element 10 and the first or secondmagnetic disc 1 or 15. As the result of the fact that the head slider216 and the magnetic head element 10 move on the first or secondmagnetic disc 1 or 15 in the state floating from the first or secondmagnetic disc 1 or 15, abrasion and/or damage of the first and secondmagnetic discs 1, 15 and the magnetic head element 10 can be prevented.

[0125] When the floating type head slider 216 constituted in this way isused, even in the case where there are slight uneven portions at thesurface of the first or second magnetic disc 1 or 15 as shown in FIG.20, this head slider absorbs the influence of these uneven portions,thereby making it possible to maintain substantially constant, at thetime of recording and/or reproduction, floating quantity from the firstor second magnetic disc 1 or 15 of the head slider 216 and the magnetichead element 10. Thus, recording and/or reproduction of information canbe carried out with fixed recording and/or reproduction characteristic.

[0126] The operation for loading the first or second disc cartridge 101or 102 with respect to the magnetic disc unit 201 will now be described.

[0127] In order to allow the first or second disc cartridge 101 or 102to undergo loading with respect to the magnetic disc unit 201, the firstor second disc cartridge 101 or 102 is inserted into the casing 202through the insertion/withdrawal hole 200 with one side surface wherethe cover body 107 is provided being as insertion end as shown in FIG.17.

[0128] When the first or second disc cartridge 101 or 102 is insertedinto the casing 202, the opening/closing pin 110 constituting theopening/closing mechanism disposed at the magnetic disc unit 201 side isengaged with the opening/closing pin engagement portion 111 provided atthe cover body 107 as shown in FIG. 21. At this time, the lock member112 is caused to undergo pressing operation by the opening/closing pin110. Thus, engagement with respect to the cover body 107 of the lockmember 112 is released, resulting in the state where the cover body 107can be rotated with the support shaft 108 being as the center.

[0129] As shown in FIG. 18, the opening/closing pin 110 is movablysupported along one side surface 200 a of the casing 202 and is attachedthrough a movement lever 231 caused to undergo movement biasing towardthe insertion/withdrawal hole 200 side in the direction indicated byarrow X₁ in FIG. 18 by an tension spring 230.

[0130] Further, when the first or second disc cartridge 101 or 102inserted into the casing 202 is further inserted toward the internalside of the casing 202, the opening/closing pin 110 is pushed by thecartridge body 105, and is moved in the direction indicated by arrow X₂in FIG. 22 against biasing force of the tension spring 230 while beingguided by a movement guide groove 403 formed at one surface 200 a of thecasing 202. The movement guide groove 403 for guiding movement directionof the opening/closing pin 110 is composed of an inclined groove portion404 and a horizontal groove portion 405 as shown in FIGS. 21 and 23.

[0131] The opening/closing pin 110 is adapted so that in the initialstate where it is pushed by the first or second disc cartridge 101, 102inserted into the casing 202, it is moved in rising direction whilebeing guided by the inclined guide groove 404 of the movement guidegroove 403. When the opening/closing pin 110 is moved in risingdirection, the cover body 107 is rotated in the direction indicated byarrow Y₁ in FIG. 23 with the support shaft 108 being as the centeragainst biasing force of the spring member to open the head insertionopening portion 106 provided at one side surface of the cartridge body105.

[0132] When the first or second disc cartridge 101 or 102 is furtherinserted into the casing 202 so that the opening/closing pin 110 ismoved up to the upper end portion of the inclined guide groove 404, thehead insertion opening portion 106 provided at the cartridge body 105 isfully opened.

[0133] Further, when the first or second disc cartridge 101 or 102 isfurther inserted into the casing 202, the opening/closing pin 110 ismoved within the horizontal groove portion 405 of the movement guidegroove 403. The first or second disc cartridge 101 or 102 is furtherinserted into the casing 202 while maintaining the state where the headinsertion opening portion 106 is fully opened, and is loaded withrespect to the cartridge loading portion 204 constituted on the base 211after undergone positioning. At this time, the first or second magneticdisc 1 or 15 accommodated within the cartridge body 105 is clamped by adisc table 205 a of the disc rotational operation mechanism 205,resulting in the state rotatable in one body with the disc table 205 a.Further, the rotational arm 213 which has supported the head slider 216of the magnetic head unit 210 through the head insertion opening portion106 is inserted into the cartridge body 105.

[0134] In this example, the movement lever 213 which has supported theopening/closing pin 110 is supported at one side surface 200 a of thecasing 202 so that the opening/closing pin 110 can be moved along themovement guide groove 403.

[0135] Moreover, in the vicinity of the insertion/withdrawal hole 200within the casing 202, specification information discriminationmechanism 100 is provided although not shown. This specificationinformation discrimination mechanism serves to discriminate kind of disccartridge loaded with respect to the magnetic disc unit 201. Thus,operation mode corresponding to disc cartridge to be loaded can beselected.

[0136] When the first or second disc cartridge 101 or 102 is loaded withrespect to the magnetic disc unit 201 by an operation as described aboveto carry out recording and/or reproduction of information with respectto the first or second magnetic disc 1 or 15 accommodated within thedisc cartridge 101 or 102 thereafter to operate the eject mechanismprovided at the magnetic disc unit 201, the loaded first or second disccartridge 101 or 102 is taken out from the casing 202 through theinsertion/withdrawal hole 200. At this time, the cover body 107 providedat the cartridge body 105 undergoes biasing force of the spring member,whereby it is rotated with the support shaft 108 being as the center soas to close the head insertion opening portion 106, and is locked withrespect to the lock member 112 to hold the head insertion openingportion 106 in a closed state.

[0137] Within the above-described first disc cartridge 101, the firstmagnetic disc 1 on which uneven pit trains are formed in the controlsignal recording areas 3 and control signals for controlling themagnetic head unit are recorded therewithin is accommodated. However,the first magnetic disc 1 may be a disc adapted so that magnetic layeris only formed on the surface of the disc substrate having flat surfacewithout recording control signals, etc. in advance.

Industrial Applicability

[0138] As described above, in accordance with this invention, in themagnetic disc apparatus using magnetic disc where recording and/orreproduction are carried out by the magnetic head unit which undergoesfloating force by air flow produced as the result of the fact that themagnetic disc is rotated, there are selectively loaded the first disccartridge within which there is accommodated first magnetic disc adaptedso that flat recording tracks are provided at the disc substrate formedby molding synthetic resin and magnetic layer is provided in a manner tocover recording tracks, and the second disc cartridge within which thereis accommodated second magnetic disc adapted so that information unevenpit trains are formed at the disc substrate formed by molding syntheticresin and magnetic layer is formed in a manner to include the bottomsurfaces and the upper surfaces of information uneven pit trains, themagnetic layer being magnetized in the state where magnetizationdirection of the magnetic layer portions of the bottom surfaces and thatof the magnetic layer portions of the upper surfaces of the informationuneven pit trains are different from each other so that information suchas program, etc. for controlling computer are recorded. Accordingly, byexchanging only the disc cartridge, it is possible to carry out installoperation of new program information or recording operation ofprocessing information processed by computer.

[0139] Particularly, since the magnetic disc apparatus according to thisinvention is adapted to selectively carry out loading of mass produciblemagnetic discs on which information such as program information, etc.are recorded in advance to permit implementation of install operation ofnew program information with respect to computer, operating ability ofcomputer can be improved. In addition, since install operation of newprogram information and/or recording operation of processing informationprocessed by computer can be carried out by single apparatus,information processing equipment such as computer, etc. can become morecompact.

1. A magnetic disc apparatus comprising: a disc rotational operationmechanism for allowing a magnetic disc to undergo rotational operation;a magnetic head unit comprising a magnetic head element for scanning asignal recording area of the magnetic disc caused to undergo rotationaloperation by the disc rotational operation mechanism along inner andouter circumferential directions and provided at a slider whichundergoes floating force by air flow produced as the result of the factthat the magnetic disc is rotated; and a cartridge loading portionadapted so that there is loaded a disc cartridge within which themagnetic disc caused to undergo rotational operation by the discrotational operation mechanism is accommodated, wherein there areselectively loaded, with respect to the cartridge portion, a first disccartridge within which there is accommodated a first magnetic discincluding a disc substrate formed by molding synthetic resin and adaptedso that flat recording tracks are provided on at least one surface ofthe disc substrate and a magnetic layer is provided in a manner to coverthe recording tracks, and a second disc cartridge within which there isaccommodated a second magnetic disc including a disc substrate formed bymolding synthetic resin and adapted so that information uneven pittrains are formed on at least one surface of the disc substrate and amagnetic layer is formed in a manner to include bottom surfaces andupper surfaces of the information uneven pit trains, the magnetic layerbeing magnetized so that magnetization direction of the magnetic layerportions on the bottom surfaces of the information uneven pit trains andthat of the magnetic layer portions on the upper surfaces thereof aredifferent from each other so that information are recorded on the secondmagnetic disc.
 2. A magnetic disc apparatus as set forth in claim 1,wherein uneven pit trains for control where control signals forcontrolling positions with respect to the first disc of the magnetichead unit are recorded are formed on at least one surface of the discsubstrate of the first magnetic disc.
 3. A magnetic disc apparatus asset forth in claim 1, wherein control signals for controlling positionswith respect to the first magnetic disc of the magnetic head unit arerecorded on a flat surface of the surface portion where the recordingtracks are provided of the first magnetic disc.
 4. A magnetic discapparatus as set forth in claim 1, wherein guard band portions ofrecessed lines are provided along the recording tracks on the discsubstrate of the first magnetic disc.
 5. A magnetic disc apparatus asset forth in claim 1, wherein the information pit trains and uneven pittrains for control where control signals for controlling positions withrespect to the second disc of the magnetic head unit are recorded areformed on at least one surface of the disc substrate of the secondmagnetic disc.
 6. A magnetic disc apparatus as set forth in claim 1,wherein information uneven pit trains are formed at one surface of thedisc substrate of the second magnetic disc and a magnetic layer isformed in a manner to include bottom surfaces and upper surfaces of theinformation uneven pit trains, the magnetic layer being magnetized sothat magnetization direction of the magnetic layer portions on thebottom surfaces of the information pit trains and that of the magneticlayer portions on the upper surfaces thereof are different from eachother, flat recording tracks being provided on the other surface of thedisc substrate, a magnetic layer being provided in a manner to cover therecording tracks.
 7. A magnetic disc apparatus as set forth in claim 1,wherein the magnetic disc apparatus comprises a base adapted so that atleast the disc rotational operation mechanism and the magnetic head unitare attached and a cartridge loading portion is provided, and a casingwithin which the base is accommodated, and wherein aninsertion/withdrawal hole of the disc cartridge is provided at thecasing, and the disc cartridge inserted into the casing through theinsertion/withdrawal hole is loaded with respect to the cartridgeloading portion.
 8. A magnetic disc apparatus as set forth in claim 7,wherein the magnetic disc apparatus further comprises, within thecasing, a cover opening/closing mechanism for allowing a cover bodywhich opens or closes an opening portion provided at the disc cartridgeto undergo opening operation.
 9. A magnetic disc apparatus as set forthin claim 7, wherein the magnetic disc apparatus further comprises acartridge discrimination mechanism for discriminating kind of the disccartridge loaded with respect to the cartridge loading portion.
 10. Amagnetic disc adapted so that recording and/or reproduction are carriedout by a magnetic head unit comprising a magnetic head element providedat a slider which undergoes floating force by air flow produced as theresult of the fact that the magnetic disc is rotated, the magnetic disccomprising: a disc substrate formed by molding synthetic resin andadapted so that information uneven pit trains where information arerecorded and uneven pit trains for control where control signals forcontrolling positions of the magnetic head unit are recorded are formedat least one surface; and a magnetic layer formed in a manner to includebottom surfaces and upper surfaces of the information uneven pit trainsand the control uneven pit trains, wherein the magnetic layer ismagnetized so that magnetization direction of the magnetic layerportions on bottom surfaces and that of the magnetic layer portion onupper surfaces of the information uneven pit trains are different fromeach other so that information are recorded, and the magnetic layer isfurther magnetized so that magnetization direction of the magnetic layerportions on bottom surfaces and that of the magnetic layer portions ofupper surfaces of the control uneven pit trains are different from eachother so that control signals are recorded.
 11. A magnetic disc as setforth in claim 10, wherein the information uneven pit trains whereinformation are recorded and the control uneven pit trains where controlsignals for controlling positions of the magnetic head unit are recordedare formed on both surfaces of the disc substrate.
 12. A magnetic disccomprising: a disc substrate adapted so that information uneven pittrains where information are recorded and uneven pit trains for controlwhere control signals for controlling positions of the magnetic headunit are recorded are formed on one surface, and flat recording tracksare provided at the other surface; a magnetic layer formed in a mannerto include bottom surfaces and upper surfaces of the information unevenpit trains and the control uneven pit trains formed on one surface ofthe disc substrate; and a magnetic layer formed in a manner to coverrecording tracks formed on the other surface of the disc substrate,wherein the magnetic layer formed on one surface of the disc substrateis magnetized so that magnetization direction of the magnetic layerportions on the bottom surfaces and that of the magnetic layer portionson the upper surfaces of the information pit trains are different fromeach other so that information are recorded, and that magnetic layerportion is magnetized so that magnetization direction of the magneticlayer portions on the bottom surfaces and that of the magnetic layerportions of the upper surfaces of the control uneven pit trains aredifferent from each other so that control signals are recorded.
 13. Amagnetic disc apparatus as set forth in claim 12, wherein uneven pittrains for control where control signals for controlling position of themagnetic head unit are recorded are formed at the other surface of thedisc substrate.
 15. A magnetic disc as set forth in claim 10, whereinguard band portions of recessed lines are provided on the disc substratealong the information pit trains.
 16. A magnetic disc as set forth inclaim 10, which comprises a hub mechanism including a pair of holdingmembers attached to the disc substrate in the state where the peripheraledge of a center hole provided at the central portion of the discsubstrate is put therebetween, and a clamping member of steel attachedto the holding members and clamped by a disc rotational operationmechanism, wherein the pair of holding members of the hub mechanism areformed by synthetic resin having substantially the same coefficient ofthermal expansion as that of the disc substrate.
 17. A magnetic disc asset forth in claim 16, wherein the disc substrate and the pair ofholding members are formed by synthetic resin having coefficient ofthermal expansion of 6.5 to 7.5×10⁻⁵ deg⁻¹.
 18. A disc cartridgecomprising: a cartridge body within which there is rotatablyaccommodated either one of a first magnetic disc adapted so that flatrecording tracks are provided at least at one surface of a discsubstrate formed by molding synthetic resin and a magnetic layer isprovided in a manner to cover the recording tracks, the first magneticdisc being adapted so that recording and/or reproduction are carried outby a magnetic head unit comprising a magnetic head element provided at aslider which undergoes floating force by air flow produced as the resultof the fact that the magnetic disc is rotated, and a second magneticdisc adapted so that there are provided a disc substrate formed bymolding synthetic resin and such that information uneven pit trainswhere information are recorded and uneven pit trains for control wherecontrol signals for controlling positions of the magnetic head unit arerecorded are formed on at least one surface, and a magnetic layer formedin a manner to include bottom surfaces and upper surfaces of theinformation uneven pit trains and the control uneven pit trains, themagnetic layer being magnetized in the state where magnetizationdirection of the magnetic layer portions on the bottom surfaces and thatof the magnetic layer portions of the upper surfaces of the informationuneven pit trains are different from each other so that information arerecorded, the magnetic layer being further magnetized in the state wheremagnetization direction of the magnetic layer portions on the bottomsurfaces and that of the magnetic layer portions of the upper surfacesof the control uneven pit trains are different from each other so thatcontrol signals are recorded, the second magnetic disc being adapted sothat recording and/or reproduction are carried out by a magnetic headunit comprising a magnetic head element provided at a slider whichundergoes floating force by air flow produced as the result of the factthat the magnetic disc is rotated; an opening portion for insertion ofthe magnetic head unit provided at one side surface of the cartridgebody; a cover body for opening/closing the opening portion; and acentral opening portion which allows at least the central portion of themagnetic disc to be faced to the external.
 19. A disc cartridge as setforth in claim 18, wherein the opening portion is provided at the frontof insertion direction side into the magnetic disc apparatus of thecartridge body.
 20. A disc cartridge as set forth in claim 18, whereinthe cover body is rotatably supported with respect to the cartridge bodyso that it can be rotated in a direction in parallel to plane surface ofthe cartridge body, and is biased by a biasing member in a direction toclose the opening portion.
 21. A disc cartridge as set forth in claim20, wherein an engagement portion engaged with a cover body openingmember provided at the magnetic disc apparatus side when the disccartridge is inserted into the magnetic disc apparatus is provided atthe cover body.
 22. A disc cartridge as set forth in claim 19, whereinthe cover body is rotatably supported with respect to the cartridge bodyso that it can be rotated in a direction perpendicular to plane surfaceof the cartridge body, and is biased by a biasing member in a directionto close the opening portion.
 23. A disc cartridge as set forth in claim18, wherein a discrimination portion for discriminating kind of themagnetic disc accommodated within the cartridge body is provided at thecartridge body.
 24. A disc cartridge as set forth in claim 18, whichcomprises a hub mechanism including a pair of holding members attachedto the magnetic disc in the state where the peripheral edge of a centerhole provided at the central portion of the magnetic disc is put or heldtherebetween, and a clamping member of steel attached to the holdingmembers and clamped by the disc rotational operation mechanism, whereinthe pair of holding members of the hub mechanism are formed by syntheticresin having substantially the same coefficient of thermal expansion asthat of the disc substrate constituting the magnetic disc.
 25. A disccartridge as set forth in claim 24, wherein the disc substrate and thepair of holding members are formed by synthetic resin having coefficientof thermal expansion of 6.5 to 7.5×10⁻⁵ deg⁻¹.
 26. A disc cartridge asset forth in claim 18, wherein uneven pit trains for control wherecontrol signals for controlling position with respect to the first discof the magnetic head unit are recorded are formed at least at onesurface of the disc substrate of the first magnetic disc.
 27. A disccartridge as set forth in claim 18, wherein control signals forcontrolling position with respect to the first magnetic disc of themagnetic head unit are recorded on a flat surface of the surface portionwhere recording tracks are provided of the first magnetic disc.
 28. Adisc cartridge as set forth in claim 18, wherein the information pittrains and uneven pit trains for control where control signals forcontrolling positions with respect to the second disc of the magnetichead unit are recorded are formed at least at one surface of the discsubstrate of the second magnetic disc.
 29. A disc cartridge as set forthin claim 18, wherein information uneven pit trains are formed at onesurface of the disc substrate of the second magnetic disc and a magneticlayer is formed in a manner to include bottom surfaces and uppersurfaces of the information uneven pit trains, the magnetic layer beingmagnetized in the state where magnetization direction of the magneticlayer portions on the bottom surfaces and that of the magnetic layerportions of the upper surfaces of the information pit trains aredifferent from each other so that information are recorded, flatrecording tracks being provided on the other surface of the discsubstrate, a magnetic layer being provided in a manner to cover therecording tracks.